Optical sighting device



Aug. 1, 1961 H. A. WAGNER OPTICAL SIGHTING DEVICE 3 Sheets-Sheet 1 Filed June 28, 1955 Fig./

INVENTOR. HERBERT A. WAGNER A757'0R/v; Y f

8- 1, 1961 H. A. WAGNER 2,994,245

OPTICAL SIGHTING DEVICE Filed June 28, 1955 3 Sheets-Sheet 2 INVENTOR. HERBERT A. WAGNER Aug. 1, 1961 H. A. WAGNER OPTICAL SIGHTING DEVICE Filed June 28, 1955 3 Sheets-Sheet 5 INVENTOR.

A. WAGNER 'ATTORNE? Unite This invention relates to visual guidance systems and more particularly to a method and an optical sighting device for guiding missiles or the like which employs a mirror system for determining the visual angle between a target and a missile.

Numerous types of control systems have been pro posed for missile guidance, and this invention concerns one of those types commonly referred to as a command system wherein the path of the missile can be changed after launching by directing signals from some remote control station. In one variation of this type, the directing signals may be derived by one or more radar systems which track the target and missile to obtain the necessary values of elevation, azimuth and range. Another variation employs a missile having television to send back to the control station a picture of the target to enable an operator to keep the missile on the target. These systems necessarily entail a complex and heavy construction which are practically limited in use to ground installatrons.

According to the present invention, a dual line of sight guidance system is provided utilizing a sighting device which is small, compact, and readily adapted for use in, but not restricted to, confined installations, for example, in the cockpit of a fighter plane or in a tank. The sighting device generally comprises a pluralityof flat reflecting surfaces adapted to be disposed in a parallel arrangement, one of said mirrors being movable to provide values of azimuth and elevation components of the error angle, that is, the angle between the missile and target sight lines. The movable mirror is mounted on a resilient support and is actuated by an electromagnetic system controlled by the sight operator. To carry out the guidance method, a substantially monochromatic flare is attached to the missile and the sight is provided with two filters, one for each line of sight. One filter transmits substantially only the monochromatic light and the other filter absorbs substantially all of said monochromatic light thereby a light image of the target in one line of sight and a light image of the missile in the other line of sight may be compared to determine the error angle. A demagnifying lens system is mounted to the front of the sight for movement into the missile line of sight when it is desired to reduce the required mirror movement.

A principal object of this invention is to provide a visual sighting method employing dual lines of sight and capable of distinguishing a single combined image of the missile and target.

A further object is to provide a sighting device which can measure small and large error angles.

,Another object is to provide a sighting device employing a movable mirror system for continuously measuring azimuth and elevation components of the error angle; and to provide such a mirror system which is fast in response, that has a minimum of lost motion, and that can be remotely controlled.

Still a further object is to provide a sighting device which is simple in construction, compact, and capable of being installed in confined installations.

Other objects and many of the atttendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following fitates Patent ror mounting and balance mechanism taken along line lV-IV of FIG. 3; and

FIG. 5 is a bottom plan view of the mirror mounting showing the disposition of the magnets and leaf spring taken along line VV of FIG. 3.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown generally in FIG. 1 a simplified diagrammatic view of a sighting device '10 with the optical components shown schematically to explain the principle of sight operation. The sight utilizes two lines of sight, each of which will include light from the target T and light from the missle M one line of sight being designated by broken line 11, and one designated by broken line 13. Any angle between these lines of sight is the error angle between the position of the missile and target. The designation of the lines of sight to the target and missile are arbitrary, and the manner of selection will be presently described. Sight 10 comprises.

at least two flat mirrors one for each of the lines of sight, one mirror being preferably a fixed mirror and the other mirror being a movable mirror, being represented by 12 and 14, respectively. Both mirrors may be disposed substantially in parallel planes so that any angular displace. ment between the mirrors from their parallel disposition necessary to maintain the missile and target images in.

matched relation will be a measurement of the error angle. The particular mounting and actuating means for movable mirror 14 will be later described.

'One of said mirrors is a half silvered or translucent mirror capable of transmitting light as well as reflecting light, and, as a practical matter to simplify the sight design it is preferred that fixed mirror 12 be the translucent mirror. The sight observer 16 is in a position providing a direct view of the target, and an indirect or reflected view of the missile from mirror 14 and mirror 12. However, such a relation is not critical since an indirect view of both target and missile can be achieved by positioning the observer at a position degrees counterclockwise as. viewed in FIG. 1.

A telescope 18 of a conventional design and having any desired power, e.g. 6 power, is provided for observer 16 and mounted on the sight, and since only one eye of the observer is needed the telescope may be a monocular type. Having one eye free, the observer can directlhis;

two lines of sight is accomplished by providing the missile with a flare emitting a substantially monochromatic light, such as a sodium light, and by employing suitable filters in the two lines of sight. For example, to ensure a view in the device of only the missile in line of sight '13, a pass filter 20 is inserted in the line of sight which will pass substantially only the yellow light of the missile flare,

and, to provide a view in the device of only the target in periscope arrangement line-ofsight 11am absorption filter 22, which may be'a didymiu-m filter, is inserted in the line of sight 1 1 to abso rb substantially all of the yellow sodium lines of the missile flare. An absolute separation of the target and missile in the two lines of sight will occur only if perfect flares and filters are available, but even in the absence of such, the operator will be able to track the desired target and missile images if the filters are able to substantially accomplish their purpose. As a matter of design, absorption filter 22 and fixed mirror 12 can be constructed as a single element.

A de-magnifier unit 24, shown in FIG. 1 as a binocular telescope of conventional design, may be moved into the lines of sight in front of the sight to obtain a larger field of view and to measure larger error angles with a given movement of the movable mirror as required during missile launching. The net amplification of the entire system will be the product of the powers of the telescope and the de-magnifier. As a rule, the de-magnification is chosen smaller than the power of the magnifying telescope, eg. 1:8 power during launching and diminished thereafter to about 1:3 power. For some applications a monocular telescope may be employed as a demagnifier movable in and out of the indirect view, as illustrated in FIGS. 2 and 3.

A preferred embodiment of sight is shown in FIGS. 2 to 5, and comprises an outer sight case 28 having a removable cover 29 formed with a front window 30. The various sight components in the case are mounted on a base 34 and the entire unit supported in an airplane cockpit or other installation by a threaded bushing 36. The bushing also functions as a conduit for the electrical conductors, not shown, entering the case. Monocular telescope 18 is secured to base 34 by a bolt 38 in a position Where an eyepiece 40 projects rearwardly through a case opening 42 for access by the observer. The case is constructed with a triangular top wall (FIG. 2) so that the observers eye not occupied in sighting through telescope 18 has an unobstructed View ahead of the sight for purposes of observation. Absorption filter 22 is disposed in the line of sight being supported at the edges in opposed slots 44 formed in a pair of spaced upright brackets 46 mounted on base 34. Filter 22 is clamped in the bracket slots by set screws 48 being resiliently backed by compression coil springs 50 to permit parallel alignment of mirrors 12 and 14. As previously described, half mirror 12'may be integrally formed with filter 22, such as by silvering the backportion thereof. Pass filter is disposed in the line of sight 13 by a bracket, not shown, mounted to base 34.

The manner of universally mounting and selectively actuating the movable mirror is an important feature of the invention. As shown in FIGS. 2 to 5, mirror 14 is frictionally supported bylugsSl (FIG. 3), or may be cemented (FIG. 4) or otherwise attached centrally on a spider plate 52 which is resiliently supported on base 34 through an I shapedleaf spring 54. One spring-end is secured to spider 52 by bolts 56, the head of the bolt freely projecting into a base recess 34:: (FIG. 3), and the other spring end being secured to base portion 34 by bolts 58. Spider 52 is made of a non-magnetic material, such'as aluminum, to avoid'interference with an electromagnetic system foractuating the mirror, presently to be described. An intermediate portion 60 of leaf spring is greatly reduced in thickness to provide a'fiexible torsion connection, and a thickness of approximately .0165 inch has been found to provide suflicient mirror movement. Spider 52 is formed with a central opening 62 (FIGS. 3 and 4) to permit access to spring 54-.

Mirror 14 is selectively moved with respect to fixed mirror 12 to reflect line of sight '13 by a plurality of electromagnetic actuators, preferably, four actuators equally spaced around and connected to spider 52. Each actuator includes a coil 64 and a permanent magnet 66 in operative relation, and as each actuator canbe identical in construction' adescription' ofone' should suflice. Each coil 64 (FIG. 3) is wound in a recessed side wall of an inverted cup-shaped form 68, which may be constructed of aluminum, having a central stud 70 which projects through a corresponding aperture 72 in a spider 52 and secured thereto by a nut 74. The coil ends are soldered to lead pins 76 (FIG. 2) anchored in insulators 78 seated in the coil form and connected to conductors 7'7. The side walls of form 68 bearing the coils extend freely through a circular opening 79 (FIG. 3) between the outer and inner pole pieces 80 and 82 respectively and with permanent magnets 66 may be frictionally supported within a recess 84 in base 34. Magnet 66 is formed with a circular groove 86, aligned with opening 79, into which field the coil extends and moves when energized. Each pair of diametrically opposed coils are connected by conductors 77 in series, but one coil of each pair is wound in an opposite direction to provide an equal but opposite push-pull movement about the mirror pivot point, namely, spring 54. The amount of mirror deflection is controlled by the current flowing through the coils, which may be remotely controlled through a potentiometer, not shown. The foregoing mirror support and actuating system eliminates backlash, friction, and hunting, which results in a more accurately controlled mirror movement.

A mass block 88 shown in FIGS. 3 and 4 enables the suspended mirror system to be balanced about two horizontal axes and a vertical axis normal thereto. Block 88 is attached centrally to spider 52 by screws 90 threaded in block extensions 91 which freely extends through openings 92 in base 34. One set of balance screws 94 are adjustably threaded into block 88 to balance the mirror assembly about one axis through the center of spring 54. Two additional balance screws 96 and 98 (FIG. 3) are adjustably threaded into the block 88 to balance the mirror about the other two orthogonal axes passing through the center of spring '54.

.A plurality of securing blocks 99 (FIGS. 3 and 5), one or each coil, are mounted on base 34 and capable of sliding under the spider projections and engaging coil forms- 68 to brake the mirror assembly against damage by shock such as may occur during installation or stowage.

As previously noted with respect to FIG. 1, demagnifier unit 24 is provided in front of the sight to enable a larger field of view when necessary. Although a binocular demagnifier is shown in FIG. 1 for the two lines of sight, a monocular telescope, 100 as shown in FIGS. 2 and 3, may be used for some applications in only the in direct view in line of sight 13. Demagnifier unit 24 comprises a frame 101 constructed like a bell crank being pivoted to base 34 at 102, and having one arm 104 terminating in a split clamp 166 to support telescope 100. Another frarne arm 108 is capable of engaging a detent 1 10 to lock the demagnifier unit in an operative position, as shown in FIG. 3, where the axis of telescope 100 is aligned with movable mirror 14 in the line of sight 13. Frame 101 is manually actuated to an operative position by a crank assembly 112 (FIG. 3) against the tension of a return spring 114 which biases the de-magnifier unit to the inoperative position as shown in FIG. 2 when the detent is actuated. Crank assembly 112 comprises a shaft 116 rotatable in suitable bearings 11-8 supported on a bottom wall of cover 29, shaft 116 terminating in a handle 120 disposed in front of case 29 in a position accessible to the hand of the sight operator and having in the inner end an arm 122 pinned to the shaft and adapted to engage and lift the de-magnifier unit (as shown in broken line in FIG. 3) to the operative position when handle 120 is actuated. Detent can be the end of an armature of a solenoid 124 de-energizable by the operator to release arm 108 and permit the de-magnifier unit to be returned by spring 114 to the inoperative position. In the operation of the sight, both the targetand missile are observed by the operator through telescope 18 using when necess'ary tie-magnifier 24 in the line of sight '13. Depending on the quality of the flares and filters, the observer sees the target predominately in one line of sight and the missile predominately in the other line of sight. Any observed angle between missile flare and target is the error angle. Movable mirror 14 is electromagnetically actuated to measure the azmu-th and elevation components of this error angle, and this information is then transformed into the proper radio signals for guiding the missile along the line of sight between the observer and the target. The manner of controlling the current to the electromagnetic system for actuating the mirror, and the guidance loop does not form a part of this invention.

The sight of this invention alTords a simple and compact construction particularly suitable for use in confined installations. The sight is easy to use permitting one eye of the observer to be always free for scanning which enables the sight to be directed prior to launching without losing the ability to observe simultaneous activities of the enemy. One of the advantages of the sight resides in the use of a de-magnifier unit, permitting the ratio between the mirror motion and the measured error to be varied by changing the ocular lens of the de-magnifier, which can be done during an attack. Mounting the movable mirror system on a torsion spring eliminates all backlash, friction, and noise. The electromagnetic means for actuating the mirror system eliminates mechanical connections and enables the mirror to respond practically without a time delay.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A sighting device in a guidance system for missileto-target objects having different light emission characteristics which comprises a frame, a pair of spaced apart mirrors mounted on the frame, each mirror having a flat reflecting surface adapted to be disposed in parallel arrangement, means for movably mounting one of said mirrors to provide a universal movement for changing the angular relation between said surfaces, one of said mirrors also being capable of transmitting light, filter means for transmitting substantially only the light of one of said objects, a second filter means for absorbing substantially only the light of said one object to permit the light of each object to be visible for comparison, a monocular telescope laterally disposed on one side of said mirrors and a de-magnifier lens disposed on the other side of said mirrors, said de-magifying lens being pivotally mounted to the frame for movement in and out of one of the lines of sight to said objects.

2. A movable mirror assembly comprising a mirror, a mirror mounting, a base, resilient means for supporting the mirror mounting to the base for universal movement about a plurality of axes, electromagnetic means for including a plurality of magnets mounted to the base in spaced relationship around said mirror, a plurality of electric coils supported from said mirror mounting, each coil disposed in operative relation in the field of a corresponding magnet, whereby the mirror may be deflected to a preselected position by controlling the current to said coils.

3. The mirror assembly of claim 2 wherein said resilient means comprises a torsion spring.

4. The mirror assembly of claim 2 wherein is provided a means for balancing said mirror around the axes of movement.

5. A movable mirror assembly comprising a mirror, a mirror mounting, a base, a resilient torsion means for supporting the mirror mounting to the base for universal movement about a plurality of axes, electromagnetic means for deflecting the mirror, said electromagnetic means including a plurality of magnets mounted to the base in spaced relation around said mirror, a plurality of pairs of electric coils supported from said mirror mounting each disposed in operative relation in the field of a corresponding magnet, oppositely arranged coils of each pair being electrically connected to provide a simultaneous push-pull action in deflecting the mirror in any desired direction.

6. In a sight device for a guidance system, a movable mirror assembly comprising a mirror, a mirror mounting, a base, a torsion leaf spring for supporting the mirror centrally mounted to the base for universal movement about a plurality of axes, one end of the spring attached to the base, electromagnetic means for deflecting the mirror against the action of the spring, said electromagnetic means including at least two pairs of magnets mounted to the base in spaced relation around said mirror, the magnets of each pair being oppositely disposed, corresponding pairs of electric coils supported from said mirror mounting each in operative relation to a corresponding magnet, the coils in each pair being electrically connected in series and wound in an opposite direction whereby the coil of one pair is repelled from its magnet while the other coil of the one pair is attracted to its magnet for pivoting the mirror about said spring, and adjustable means for balancing said mirror about the axes of movement.

7. A sighting device for a missile guidance system, said missile having 'a different light characteristic from that of a target, said device having two optical paths the light from said target and the light from said missile being included in the light reaching the device along each optical path, said optical paths having different light transmission characteristics including means for permitting substantially only light of the missile to be visible in one of said optical paths, light of the target being visible in the other optical path, a pair of spaced, apart mirrors having flat reflecting surfaces, means for movably mounting one of said mirrors to provide a universal movement for reflecting only the light in one of said optical paths, one of said mirrors also being a partial mirror for reflecting the light in one of said optical paths and transmitting the light in the other optical path, said movable mirror being capable of changing the angular relation between the mirror surfaces in accordance with the relative movement of the missile to the target in any direction and for bringing the light image of the missile in one of the optical paths and the light image of the target in the other optical path into substantial coincidence.

8. A sighting device for a missile guidance system, said missile having a different chromatic characteristic from that of a target, said device having two optical paths the light from said target and the light from said missile being included in the light reaching the device along each optical path, said optical paths having different light transmission characteristics including a narrow pass filter for permitting substantially only light of the missile to be visible in one of said optical paths, light of the target being visible in the other optical path, a pair of spacedapart mirrors having flat reflecting surfaces, means for movably mounting one of said mirrors to provide a universal movement for reflecting only the light in one of said optical paths, one of said mirrors also being a partial mirror for reflecting the light in one of said optical paths and transmitting the light in the other optical path, said movable mirror being capable of changing the angular relation between the mirror surfaces in accordance with the relative movement of the missile to the target in any direction and for bringing the light image of the missile in one of the optical paths and the light image of the target in the other optical path into substantial coincidence.

9. A sighting device for a missile guidance system, said missile having a different chromatic characteristic from that of a target, said device having two optical paths the light from said target and the light from said missile being included in the light reaching the device along each optical path, said optical paths having difierent light transmission characteristics including a narrow pass filter for permitting substantially only the light of the missile to be'visible in one of said optical paths, another filter for permitting substantially only the light of the target to be visible in the other optical path, a pair of spaced-apart mirrors having flat reflecting surfaces, means for movably mounting one of said mirrors to provide a universal movement for reflecting only the light in one of said optical paths, one of said mirrors also being a partial mirror for reflecting the light in one of said optical paths and transmitting the light in the other optical path, said movable mirror being cap-able of changing the angular relation between the mirror surfaces in accordance with the relative movement of the missile to the target in any direction and'for bringing the light image of the missile in one of 'the optical paths and light image of the target in the other optical path into substantial coincidence.

10. The device of claim 9 wherein said chromatic light from the missile is a substantial monochromatic sodium light, and said another filter is a didymium filter capable of absorbing substantially all of said sodium light.

References Cited in the file of this patent UNITED STATES PATENTS Gim Sept. 20, 1955 

